This investigation is exploring the inter relationships between localized changes in intrarenal blood flow, renal function and renin- angiotensin system. Defective substrate for angiotensin formation is believed to be the underlying etiology for the renal failure of severe liver disease (hepato-renal syndrome). Current projects are concerned with elucidating the mechanism by which the renin angiotensin system affects renal blood flow, current studies are evaluating changes in renin release and intra-renal blood flow distribution, as measured by Xenon-133 washout techniques, produced by the effects of renin inhibitors, such as Propranolol, on renin release and blood flow distribution are also being evaluated. Perfusion techniques for renal preservation are being evaluated with special attention to perfusate composition on in-vitro renal function and perfusate distribution. Flurochemicals (FX-80, FC-43) dispersed in plasma can serve as red cell substitutes and are being evaluated in long term preservation and transplantation experiments. The theory that homogenous fluids such as plasma may not be optimal renal perfusates is being explored. A wide variety of microparticles added to normal plasma are being evaluated in both short normothermic and long hypothermic perfusions to evaluate effects on renal function and survival after transplantation.